Enzymes Of Fatty Acid Synthesis Research Articles

Metabolomic profiling of triple negative breast cancer cells suggests that valproic acid can enhance the anticancer effect of cisplatin.

Cisplatin is an effective chemotherapeutic agent for treating triple negative breast cancer (TNBC). Nevertheless, cisplatin-resistance might develop during the course of treatment, allegedly by metabolic reprograming, which might influence epigenetic regulation. We hypothesized that the histone deacetylase inhibitor (HDACi) valproic acid (VPA) can counter the cisplatin-induced metabolic changes leading to its resistance. We performed targeted metabolomic and real time PCR analyses on MDA-MB-231 TNBC cells treated with cisplatin, VPA or their combination. 22 (88%) out of the 25 metabolites most significantly modified by the treatments, were acylcarnitines (AC) and three (12%) were phosphatidylcholines (PCs). The most discernible effects were up-modulation of AC by cisplatin and, contrarily, their down-modulation by VPA, which was partial in the VPA-cisplatin combination. Furthermore, the VPA-cisplatin combination increased PCs, sphingomyelins (SM) and hexose levels, as compared to the other treatments. These changes predicted modulation of different metabolic pathways, notably fatty acid degradation, by VPA. Lastly, we also show that the VPA-cisplatin combination increased mRNA levels of the fatty acid oxidation (FAO) promoting enzymes acyl-CoA synthetase long chain family member 1 (ACSL1) and decreased mRNA levels of fatty acid synthase (FASN), which is the rate limiting enzyme of long-chain fatty acid synthesis. In conclusion, VPA supplementation altered lipid metabolism, especially fatty acid oxidation and lipid synthesis, in cisplatin-treated MDA-MB-231 TNBC cells. This metabolic reprogramming might reduce cisplatin resistance. This finding may lead to the discovery of new therapeutic targets, which might reduce side effects and counter drug tolerance in TNBC patients.

AMP-activated protein kinase - a journey from 1 to 100 downstream targets.

A casual decision made one evening in 1976, in a bar near the Biochemistry Department at the University of Dundee, led me to start my personal research journey by following up a paper that suggested that acetyl-CoA carboxylase (ACC) (believed to be a key regulatory enzyme of fatty acid synthesis) was inactivated by phosphorylation by what appeared to be a novel, cyclic AMP-independent protein kinase. This led me to define and name the AMP-activated protein kinase (AMPK) signalling pathway, on which I am still working 46 years later. ACC was the first known downstream target for AMPK, but at least 100 others have now been identified. This article contains some personal reminiscences of that research journey, focussing on: (i) the early days when we were defining the kinase and developing the key tools required to study it; (ii) the late 1990s and early 2000s, an exciting time when we and others were identifying the upstream kinases; (iii) recent times when we have been studying the complex role of AMPK in cancer. The article is published in conjunction with the Sir Philip Randle Lecture of the Biochemical Society, which I gave in September 2022 at the European Workshop on AMPK and AMPK-related kinases in Clydebank, Scotland. During the early years of my research career, Sir Philip acted as a role model, due to his pioneering work on insulin signalling and the regulation of pyruvate dehydrogenase.

Characterization of a Cyclic Dinucleotide Metabolic Switch to Fuel Antitumor Immunity

Chimeric antigen receptor (CAR) T cells have revolutionized the treatment of patients with relapsed and/or refractory lymphomas resulting in high response rates even in heavily pretreated individuals. Despite the efficacy of CAR T therapy in these cases, long-term disease control remains a challenge owing to the poor persistence and decreased survival of these cells in the tumor microenvironment (TME). Within the TME, CAR T cell activity and survival are impeded by increased metabolic stress from chronic stimulation, hypoxia, and limited nutrient availability. This ultimately leads to T cell exhaustion, a state characterized by dysfunctional mitochondria, decreased proliferation, and increased apoptosis. Memory T cells, particularly memory stem T cells (Tscm), are able to better adapt to the TME than effector T cells, which is in part secondary to metabolic reliance on β-oxidation of fatty acids (FAO) as opposed to glycolysis. This sustains mitochondrial ATP production and supports antioxidant pathways to limit cell stress leading to enhanced persistence and improved tumor control by Tscm. As effector T cells make up the bulk of CAR T products and Tscm are quite rare, tuning CAR T cell metabolism to enhance Tscm production could be a means to improve the long-term efficacy of cellular therapies. Our lab previously observed that treatment of mice with the mammalian cyclic dinucleotide (CDN) 2'3'-cGAMP increased the persistence and proliferation of Th/Tc17 cells expressing an anti-neu CAR in a model of locally advanced breast cancer. CDNs are evolutionarily conserved second messengers that classically activate the innate immune system in response to pathogens by binding to pattern recognition receptors, but more recent data shows that they are also important in the antitumor immune response by modulating tumor immunogenicity. We now extend those findings and show that treatment of isolated T cells with cGAMP induces a T cell intrinsic mechanism that drives Tscm formation in ex vivo expanded murine T cells. Th/Tc17 cells treated with cGAMP during their in vitro differentiation and expansion show a 5-10 fold increase in Tscm compared to control cells. This is supported by increased expression of the transcription factors Tcf7 and Lef1, which are key mediators in maintaining T cell stemness and memory. Though CDNs are thought to mediate their downstream effects mainly through activation of the adaptor protein STING (stimulator of interferon genes), our data indicates that CDNs promote T cell memory independent of canonical STING activation in Th/Tc17 cells. This may in part explain why we see minimal cytotoxicity in Th/Tc17 cells treated with cGAMP as compared to prior reports which observed STING dependent cell death following CDN exposure in other T cell subsets. Instead, CDNs activate AMPK (AMP-activated protein kinase) leading to metabolic reprogramming in Th/Tc17 cells. Total RNA sequencing data and functional studies of cellular bioenergetics point to reduced glycolytic metabolism following cGAMP treatment. Downstream of AMPK activation we also observe inhibition of acetyl-CoA carboxylase (ACC), the rate limiting enzyme in fatty acid synthesis, and upregulation of Cpt1a which is key to FAO, suggestive of enhanced fatty acid usage as a fuel source. Collectively this metabolic profile favors the production of Tscm and further work is ongoing to delineate the molecular mechanisms behind this cGAMP triggered metabolic switch. As there is increasing evidence that tumor cells secrete 2'3'-cGAMP in the TME, this pathway could be readily targeted to manipulate the bioenergetics of CAR T cells to maximize their memory potential and enhance their in vivo persistence and function.

Dysfunction of T Cells from Chronic Lymphocytic Leukemia (CLL) Patients Is Linked to Disturbed Lipid and Fatty Acid Homeostasis

Background: Successful T cell-based anti-cancer therapies require proliferation and longevity of effector cells, features that highly depend on metabolic processes. A key feature of chronic lymphocytic leukemia (CLL) is acquired T cell dysfunction, resulting in impaired proliferative capacity (van Bruggen, et al Blood Adv 2022). T cell lipid metabolism has only recently come into focus as an important source of energy production and at the same time as essential component for the formation of new membranes upon proliferation. Fatty acid (FA) and lipid uptake in T cells requires several membrane proteins, among which the scavenger FA transporter CD36 and the low-density lipoprotein receptor (LDL-R). Specifically CD36-mediated FA transport has been identified to modulate (intratumoral) Treg and cytotoxic CD8+ T cells (Kolonin, et al, 2021 Immunometab). Whether T cell lipid and FA metabolism are affected in CLL is currently unknown. Methods: Peripheral blood mononuclear cells (PBMCs) of untreated CLL patients and, as control, age-matched healthy donors (HD) were studied. T cells were analyzed by transcriptomics, lipidomics and flow cytometry, either directly after thawing or after a 2-day culture with or without αCD3/αCD28 antibodies. Results: Unbiased transcriptomic analyses of patient-derived T cells following αCD3/αCD28 activation showed reduced expression of the master regulators of FA and cholesterol biosynthesis SREBF1 and SREBF2 in the presence of autologous CLL cells. This was associated with significantly reduced protein abundance of downstream targets of the SREBP pathway, including the key enzymes in FA synthesis and saturation FASN and SCD. In accordance with these data, lipidomic analyses highlighted an altered lipid profile in T cells from CLL patients that clearly demarcated them from HD T cells. In short, unbiased analyses revealed disturbed lipid homeostasis in CLL T cells at multiple levels, which led us to investigate lipid and FA metabolic pathways and their related functional consequences. Studying lipid and FA uptake capacity revealed lower expression of the FA transporter CD36 on CLL T cells. Stimulation of HD T cells resulted in upregulation of CD36 and the main receptor for cholesterol uptake LDL-R, accompanied by increased uptake of long chain fatty acids (LCFA) and increased FA-oxidation, concomitantly with induced expression of the activation marker CD25. In contrast, CLL-derived T cells did not increase CD36 or LDL-R expression, LCFA uptake or oxidation (Fig 1 and 2). Because of a recently suggested role for CD36 in T cell function, we next specifically analyzed CD36-expressing T cells (CD36+), and found these to have higher ability for LCFA and glucose uptake, and higher expression of the glucose transporter GLUT-1 than CD36 negative T cells from the same HD. Accordingly, CD36+ cells were also more likely to increase their CD25 expression and mitochondrial mass upon a 48h stimulation. This CD36+ T cell subpopulation, with potential metabolic and functional advantage, was virtually absent in CLL PBMCs. Impact of FA and lipid metabolism on proliferation was further established by the observation that culturing of HD T cells in absence of exogenous lipids resulted in nearly absent proliferative capacity. However, despite decreased expression of lipid and FA transporters, we observed marked accumulation of lipid droplets (LD) in T cells from CLL patients, suggesting an impaired ability to mobilize lipids towards oxidation pathways or as building blocks for membranes. In line with this, we found that in contrast to HD T cells that increased the expression of the rate-limiting enzyme for lipolysis ATGL, CLL T cells failed to do so. Conclusions: We provide the first data showing a disturbed lipid and FA metabolism of CLL T cells that contributes to T cell dysfunction. This includes decreased expression of FA synthesis enzymes as well as FA and cholesterol transporters. CD36+ T cells are metabolically distinct and are largely absent in CLL. We are investigating strategies to increase FA and lipid metabolism in order to rebalance lipid homeostasis. This could ameliorate CLL T cell dysfunction and specifically proliferation defects in CLL. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Structural study of acyl carrier protein of Enterococcus faecalis and its interaction with enzymes in de novo fatty acid synthesis

Enterococcus faecalis has recently shown signs of high antibiotic resistance. These bacteria can endure extremes of temperature and this may be due to the high thermostability of its proteins. E. faecalis has two acyl carrier proteins (ACPs), AcpA (EfAcpA), which is essential for de novo fatty acid synthesis (FAS), and EfAcpB, which plays an auxiliary role in the incorporation of exogenous fatty acids. Structural studies on EfAcpA and its interaction with FAS enzymes have not yet been reported. Here, we investigated the structures of EfAcpA using NMR spectroscopy, showing that EfAcpA consists of three α-helices with a long α2α3 loop, while the other ACPs have four α-helices. CD experiments showed that the melting temperature of EfAcpA is 76.3 °C and the Ala mutation for Ile10 reduced it dramatically by 29.5 °C. Highly conserved Ile10 of EfAcpA mediates compact intramolecular packing and promotes high thermostability. A docking simulation of EfAcpA and β-ketoacyl-ACP synthase III (EfKAS III) showed that the α2α3 loop of EfAcpA contributes to specific protein–protein interactions (PPI) with EfKAS III. Unconserved charged residues, Lys52 and Glu54, in the α2α3 loop of EfAcpA formed specific electrostatic interactions with Asp 226 and Arg217 of EfKAS III, respectively. Binding interactions between EfAcpA and EfKASIII may provide insights for designing PPI inhibitors targeting FAS in E. faecalis to overcome its antibacterial resistance.

Parkinson-causing mutations in LRRK2 impair the physiological tetramerization of endogenous α-synuclein in human neurons

α-Synuclein (αSyn) aggregation in Lewy bodies and neurites defines both familial and ‘sporadic’ Parkinson’s disease. We previously identified α-helically folded αSyn tetramers, in addition to the long-known unfolded monomers, in normal cells. PD-causing αSyn mutations decrease the tetramer:monomer (T:M) ratio, associated with αSyn hyperphosphorylation and cytotoxicity in neurons and a motor syndrome of tremor and gait deficits in transgenic mice that responds in part to L-DOPA. Here, we asked whether LRRK2 mutations, the most common genetic cause of cases previously considered sporadic PD, also alter tetramer homeostasis. Patient neurons carrying G2019S, the most prevalent LRRK2 mutation, or R1441C each had decreased T:M ratios and pSer129 hyperphosphorylation of their endogenous αSyn along with increased phosphorylation of Rab10, a widely reported substrate of LRRK2 kinase activity. Two LRRK2 kinase inhibitors normalized the T:M ratio and the hyperphosphorylation in the G2019S and R1441C patient neurons. An inhibitor of stearoyl-CoA desaturase, the rate-limiting enzyme for monounsaturated fatty acid synthesis, also restored the αSyn T:M ratio and reversed pSer129 hyperphosphorylation in both mutants. Coupled with the recent discovery that PD-causing mutations of glucocerebrosidase in Gaucher’s neurons also decrease T:M ratios, our findings indicate that three dominant genetic forms of PD involve life-long destabilization of αSyn physiological tetramers as a common pathogenic mechanism that can occur upstream of progressive neuronal synucleinopathy. Based on αSyn’s finely-tuned interaction with certain vesicles, we hypothesize that the fatty acid composition and fluidity of membranes regulate αSyn’s correct binding to highly curved membranes and subsequent assembly into metastable tetramers.

Targeting de novo lipogenesis and the Lands cycle induces ferroptosis in KRAS-mutant lung cancer

Mutant KRAS (KM), the most common oncogene in lung cancer (LC), regulates fatty acid (FA) metabolism. However, the role of FA in LC tumorigenesis is still not sufficiently characterized. Here, we show that KMLC has a specific lipid profile, with high triacylglycerides and phosphatidylcholines (PC). We demonstrate that FASN, the rate-limiting enzyme in FA synthesis, while being dispensable in EGFR-mutant or wild-type KRAS LC, is required for the viability of KMLC cells. Integrating lipidomic, transcriptomic and functional analyses, we demonstrate that FASN provides saturated and monounsaturated FA to the Lands cycle, the process remodeling oxidized phospholipids, such as PC. Accordingly, blocking either FASN or the Lands cycle in KMLC, promotes ferroptosis, a reactive oxygen species (ROS)- and iron-dependent cell death, characterized by the intracellular accumulation of oxidation-prone PC. Our work indicates that KM dictates a dependency on newly synthesized FA to escape ferroptosis, establishing a targetable vulnerability in KMLC.

Relation between Acetyl-CoA Carboxylase with some Biochemical Variables in Iraqi Men with Acute Myocardial Infarction and Diabetes

Background: Acute myocardial infarction (AMI) is a widespread cause of death in numerous parts of the world. Many factors raise the risk of myocardial infarction (MI). One of the most of it is atherosclerosis, caused by many factors such as Hyperlipidemia. Acetyl-CoA carboxylase (ACC) is the key regulatory enzyme in fatty acid synthesis. The disorder of lipid metabolism is one of the characteristics of diabetes, which is considered a risk factor for MI. Therefore, the activity ACC was estimated in patients with AMI and Diabetes. Method: The study included estimation of ACC activity and correlated with other biochemical variables such as Troponin T(cTnT), C-reactive protein (CRP), glucose‚ lipid profile, electrolytes [Sodium (Na⁺), Potassium(K⁺), Chloride (Cl⁻)]‚ urea and creatinine (Crea.), and evaluation of body mass index (BMI) effect in serum of 60 patients with AMI and diabetes compared with 30 serum from apparently healthy individuals as a control group, both groups are of males with an average age (25–60 years). Results and Conclusions: Results showed a significant increase in levels of ACC, cTnT, CRP, Glucose, and Lipid profile except for high-density lipoprotein – cholesterol (HDL-C) and urea, while a significant decrease with Na⁺and K⁺ also a non-significant variation was observed with Cl⁻ and creatinine in AMI and diabetes patients compared to control group.

Response of Trypanosoma brucei to Exogenous Fatty Acids in Low Lipid Conditions

Trypanosoma brucei is an extracellular parasite that causes African Sleeping Sickness and is endemic to the sub‐Saharan African region. The parasite's extracellular nature forces the parasite to adapt to its host's environment. One of the regulatory mechanisms is to regulate fatty acid synthesis enzymes in response to exogenous fatty acids. Our previous study showed that the insect‐host procyclic form (PF) T. brucei regulates the activity and expression level of acetyl‐CoA carboxylase (ACC) when grown in media containing different lipid levels. PF in low lipid media has an elevated ACC activity but lower ACC protein level than in high lipid media. We also observed that the addition of C18:0 to PF in low lipid media reduced ACC activity and increased growth rate, which showed an environmental response to the exogenous fatty acid level. Here, we observe the growth and the ACC level of low lipid‐adapted PF T. brucei after treatment with fatty acids of different chain lengths. We did not observe a significant change in the ACC protein level; however, we observed significant growth differences with the addition of different fatty acids, and some of these effects were cell density‐dependent. These data suggested that adding fatty acids changes ACC's activity and pattern of PF growth in low lipid but does not change PF's ACC expression level. Future studies will investigate whether different fatty acids regulate ACC activity by phosphorylation, allosteric regulation, or a combination of both mechanisms.

PDK4 Inhibition Ameliorates Melatonin Therapy by Modulating Cerebral Metabolism and Remyelination in an EAE Demyelinating Mouse Model of Multiple Sclerosis.

We recently showed that melatonin ameliorates the severity of experimental autoimmune encephalomyelitis (EAE), an animal model of MS. However, efficiency of melatonin therapy was associated with side effects, manifested by slowing down of remyelination, through increasing the inhibitory effects of brain pyruvate dehydrogenase kinase-4 (PDK-4) on pyruvate dehydrogenase complex (PDC), a key enzyme in fatty acid (FA) synthesis during remyelination. In this study, we investigated the metabolic profile of FA synthesis using combination therapy of melatonin and diisopropylamine dichloroacetate (DADA), a PDK4 inhibitor, in EAE mice. Disease progression was monitored by recording the disability scores. Immunological, oligodendrogenesis and metabolic factors were also evaluated. Results showed that combination therapy of melatonin and DADA significantly reduced EAE disability scores, compared to melatonin, whereas DADA alone did not have any effect. In addition, co-therapy inhibited pro-inflammatory while increasing anti-inflammatory cytokines, significantly better than melatonin alone. Moreover, administration of combination drugs recovered the declined expression of oligodendrocytic markers in EAE, more potently than melatonin. Furthermore, co-therapy affected cerebral energy metabolism by significantly reducing lactate levels while increasing N-acetylaspartate (NAA) and 3-hydroxy-3-methyl-glutaryl-coenzyme-A reductase (HMGCR) levels. Finally, while melatonin increased lactate and PDK4 expression levels and greatly reduced PDC activity, co-therapy significantly restored PDC function while reducing the lactate levels. In summary, administration of melatonin with DADA increased the efficiency of melatonin treatment by eliminating the inhibitory effects of PDK4 on PDC’s function, a critical step for proper FA synthesis during remyelination.

Isolation and transcriptome analysis of a biotechnologically promising Black Sea protist, Thraustochytrium aureum ssp. strugatskii.

BackgroundMarine protists are an important part of the ocean ecosystem. They may possess unique sets of biosynthetic pathways and, thus, be promising model organisms for metabolic engineering for producing substances for the pharmaceutical, cosmetic, and perfume industries. Currently, full-genome data are available just for a limited number of protists hampering their use in biotechnology.MethodsWe characterized the morphology of a new cultured strain of Thraustochytriaceae isolated from the Black Sea ctenophore Beroe ovata using phase-contrast microscopy. Cell culture was performed in the FAND culture medium based on fetal bovine serum and DMEM. Phylogenetic analysis was performed using the 18S rRNA sequence. We also conducted a transcriptome assembly and compared the data with the closest species.ResultsThe protist belongs to the genus Thraustochytrium based on the 18S rRNA sequence analysis. We designated the isolated protist as T. aureum ssp. strugatskii. The closest species with the genome assembly is Schizochytrium aggregatum. Transcriptome analysis revealed the majority of the fatty acid synthesis enzymes.ConclusionOur findings suggest that the T. aureum ssp. strugatskii is a promising candidate for biotechnological use. Together with the previously available, our data would allow the establishment of an accurate phylogeny of the family Thraustochytriaceae. Also, it could be a reference point for studying the evolution of the enzyme families.

Effects of the epidermal growth factor receptor inhibitor, gefitinib, on lipid and hyaluronic acid synthesis in cultured HaCaT keratinocytes.

Epidermal growth factor receptor inhibitors (EGFRIs) are widely used for treating various cancers, including lung, colon, head and neck cancers. However, EGFRIs have unique dermatological side effects, including acneiform eruption, dry skin, paronychia and pruritus. In this study, we investigated the molecular changes induced by an EGFRI, gefitinib, in the expression of lipogenic enzymes and hyaluronic acid (HA) regulatory proteins in HaCaT keratinocytes, and whether EGF restored these changes. HaCaT cells were treated with gefitinib, with or without EGF, and treated with tumor necrosis factor α (TNFα) for inducing an inflammatory response. The mRNA and protein expression was analyzed by real-time RT-PCR, enzyme-linked immunosorbent assay (ELISA) and western blotting. Gefitinib enhanced the TNFα-induced expression of C-C motif chemokine ligand 2 (CCL2), CCL5 and C-X-C motif chemokine ligand 10 (CXCL10), and the expression of TNFα in HaCaT cells, while EGF restored these changes. At a similar concentration range, gefitinib reduced the mRNA and/or protein expression of various lipogenic enzymes for fatty acid, cholesterol and ceramide synthesis, except acidic sphingomyelinase. Gefitinib suppressed the mRNA and protein expression of HA synthase 2 (HAS2), HAS3, cluster of differentiation 44 (CD44), hyaluronidase 1 (HYAL1) and HYAL2, except the mRNA expression of HYAL1. EGF restored the changes induced by gefitinib, except for the mRNA expression of fatty acid synthase (FASN) and elongation of very long-chain fatty acid protein (ELOVL) 6. In conclusion, EGFRIs suppress lipogenesis and HA metabolism, which may contribute to adverse dermatological effects, including barrier function impairment in cancer patients treated with EGFRIs.

SGIV Induced and Exploited Cellular De Novo Fatty Acid Synthesis for Virus Entry and Replication.

Considerable attention has been paid to the roles of lipid metabolism in virus infection due to its regulatory effects on virus replication and host antiviral immune response. However, few literature has focused on whether lipid metabolism is involved in the life cycle of lower vertebrate viruses. Singapore grouper iridovirus (SGIV) is the causative aquatic virus that extensively causes fry and adult groupers death. Here, the potential roles of cellular de novo fatty acid synthesis in SGIV infection was investigated. SGIV infection not only increased the expression levels of key enzymes in fatty acid synthesis in vivo/vitro, including acetyl-Coenzyme A carboxylase alpha (ACC1), fatty acid synthase (FASN), medium-chain acyl-CoA dehydrogenase (MCAD), adipose triglyceride lipase (ATGL), lipoprotein lipase (LPL) and sterol regulatory element-binding protein-1 (SREBP1), but it also induced the formation of lipid droplets (LDs), suggesting that SGIV altered de novo fatty acid synthesis in host cells. Using the inhibitor and specific siRNA of ACC1 and FASN, we found that fatty acid synthesis was essential for SGIV replication, evidenced by their inhibitory effects on CPE progression, viral gene transcription, protein expression and virus production. Moreover, the inhibitor of fatty acid β-oxidation could also reduce SGIV replication. Inhibition of fatty acid synthesis but not β-oxidation markedly blocked virus entry during the life cycle of SGIV infection. In addition, we also found that inhibition of ACC1 and FASN increased the IFN immune and inflammatory response during SGIV infection. Together, our data demonstrated that SGIV infection in vitro regulated host lipid metabolism and, in that process, cellular fatty acid synthesis might exert crucial roles during SGIV infection via regulating virus entry and host immune response.

Dietary Supplementation with Sodium Butyrate Reduces High-sucrose Diet-induced Hepatic Accumulation of Triacylglycerols and Expression of Fatty Acid Synthesis Enzymes in Rats.

We investigated the effects of dietary supplementation with sodium butyrate (NaB) on the lipid levels, gene expression, and proteins related to lipid metabolism in nonalcoholic fatty liver disease (NAFLD) rat models fed a high-sucrose diet for 3 weeks. Supplementation with 1% and 3% NaB reduced high-sucrose-induced hepatic triacylglycerol levels and expression of genes and proteins related to fatty acid synthesis, such as fatty acid synthase and malic enzyme, in a dose-dependent manner. NaB supplementation did not affect hepatic cholesterol levels or expression of genes related to β-oxidation. NaB may prevent high-sucrose-induced NAFLD by repressing the fatty acid synthesis pathway.

Synthesis of Dolichols in Candida albicans Is Co-Regulated with Elongation of Fatty Acids

Protein glycosylation requires dolichyl phosphate as a carbohydrate carrier. Dolichols are α-saturated polyprenols, and their saturation in S. cerevisiae is catalyzed by polyprenyl reductase Dfg10 together with some other unknown enzymes. The aim of this study was to identify such enzymes in Candida. The Dfg10 polyprenyl reductase from S. cerevisiae comprises a C-terminal 3-oxo-5-alpha-steroid 4-dehydrogenase domain. Alignment analysis revealed such a domain in two ORFs (orf19.209 and orf19.3293) from C. albicans, which were similar, respectively, to Dfg10 polyprenyl reductase and Tsc13 enoyl-transferase from S. cerevisiae. Deletion of orf19.209 in Candida impaired saturation of polyprenols. The Tsc13 homologue turned out not to be capable of saturating polyprenols, but limiting its expression reduce the cellular level of dolichols and polyprenols. This reduction was not due to a decreased expression of genes encoding cis-prenyltransferases from the dolichol branch but to a lower expression of genes encoding enzymes of the early stages of the mevalonate pathway. Despite the resulting lower consumption of acetyl-CoA, the sole precursor of the mevalonate pathway, it was not redirected towards fatty acid synthesis or elongation. Lowering the expression of TSC13 decreased the expression of the ACC1 gene encoding acetyl-CoA carboxylase, the key regulatory enzyme of fatty acid synthesis and elongation.

Red Quinoa Bran Extract Prevented Alcoholic Fatty Liver Disease via Increasing Antioxidative System and Repressing Fatty Acid Synthesis Factors in Mice Fed Alcohol Liquid Diet.

Alcohol is metabolized in liver. Chronic alcohol abuse results in alcohol-induced fatty liver and liver injury. Red quinoa (Chenopodium formosanum) was a traditional staple food for Taiwanese aborigines. Red quinoa bran (RQB) included strong anti-oxidative and anti-inflammatory polyphenolic compounds, but it was usually regarded as the agricultural waste. Therefore, this study is to investigate the effect of water and ethanol extraction products of RQB on the prevention of liquid alcoholic diet-induced acute liver injury in mice. The mice were given whole grain powder of red quinoa (RQ-P), RQB ethanol extract (RQB-E), RQB water extract (RQB-W), and rutin orally for 6 weeks, respectively. The results indicated that RQB-E, RQB-W, and rutin decreased alcoholic diet-induced activities of aspartate aminotransferase and alanine aminotransferase, and the levels of serum triglyceride, total cholesterol, and hepatic triglyceride. Hematoxylin and eosin staining of liver tissues showed that RQB-E and RQB-W reduced lipid droplet accumulation and liver injury. However, ethanol extraction process can gain high rutin and antioxidative agents contents from red quinoa, that showed strong effects in preventing alcoholic fatty liver disease and liver injury via increasing superoxide dismutase/catalase antioxidative system and repressing the expressions of fatty acid synthesis enzyme acetyl-CoA carboxylase.

Roles of vitamin A in the regulation of fatty acid synthesis.

Dietary macronutrients and micronutrients play important roles in human health. On the other hand, the excessive energy derived from food is stored in the form of triacylglycerol. A variety of dietary and hormonal factors affect this process through the regulation of the activities and expression levels of those key player enzymes involved in fatty acid biosynthesis such as acetyl-CoA carboxylase, fatty acid synthase, fatty acid elongases, and desaturases. As a micronutrient, vitamin A is essential for the health of humans. Recently, vitamin A has been shown to play a role in the regulation of glucose and lipid metabolism. This review summarizes recent research progresses about the roles of vitamin A in fatty acid synthesis. It focuses on the effects of vitamin A on the activities and expression levels of mRNA and proteins of key enzymes for fatty acid synthesis in vitro and in vivo. It appears that vitamin A status and its signaling pathway regulate the expression levels of enzymes involved in fatty acid synthesis. Future research directions are also discussed.

Stabilization of fatty acid synthesis enzyme acetyl-CoA carboxylase 1 suppresses acute myeloid leukemia development.

Cancer cells reprogram lipid metabolism during their malignant progression, but limited information is currently available on the involvement of alterations in fatty acid synthesis in cancer development. We herein demonstrate that acetyl-CoA carboxylase 1 (ACC1), a rate-limiting enzyme for fatty acid synthesis, plays a critical role in regulating the growth and differentiation of leukemia-initiating cells. The Trib1-COP1 complex is an E3 ubiquitin ligase that targets C/EBPA, a transcription factor regulating myeloid differentiation, for degradation, and its overexpression specifically induces acute myeloid leukemia (AML). We identified ACC1 as a target of the Trib1-COP1 complex and found that an ACC1 mutant resistant to degradation because of the lack of a Trib1-binding site attenuated complex-driven leukemogenesis. Stable ACC1 protein expression suppressed the growth-promoting activity and increased ROS levels with the consumption of NADPH in a primary bone marrow culture, and delayed the onset of AML with increases in mature myeloid cells in mouse models. ACC1 promoted the terminal differentiation of Trib1-COP1-expressing cells and eradicated leukemia-initiating cells in the early phase of leukemic progression. These results indicate that ACC1 is a natural inhibitor of AML development. The upregulated expression of the ACC1 protein has potential as an effective strategy for cancer therapy.

Acetyl-CoA carboxylase-1/2 blockade locks dendritic cells in the semimature state associated with FA deprivation by favoring FAO.

Immunometabolism is rising as an intriguing topic that reveals the connection between immune cell function and metabolic processes. Especially, fatty acid metabolism plays an essential role in the dendritic cells (DCs) during the differentiation and maturation period. We questioned whether regulation of acetyl-CoA carboxylases 1 and 2-(ACC1/2), the core enzymes of fatty acid synthesis (FAS), would control DC function. Here, we report that blocking ACC1/2 to prevent FAS during DC maturation switched their cellular metabolism into fatty acid oxidation to fuel oxidative phosphorylation. This action turned DCs to utilize exogenous fatty acids to sustain their basal energy demand and maintain a stable cellular respiration rate. Coincidentally, under the ACC1/2 inhibitor treatment, LPS-treated DCs exhibited a semimaturation phenotype with a maturation-resistance feature, with decreased expression of costimulatory molecules including CD86 and CD40, along with the reduction of IL-12 and IL-6. The migratory capability of DCs has been known to relate to the glycolysis pathway, and here we showed that the ACC1/2 blockade did not affect the expression of CCR7 and DC migration. Furthermore, we found that under the ACC1/2 blocking condition, DCs pulsed with OVA failed to activate OVA-specific CD4+ T cell proliferation even though their antigen uptake capacity was intact. Together, our data suggest ACC1/2 as a promising target to control DC fate.

The response of Trypanosoma brucei to Exogenous Fatty Acids in Low Lipid Conditions

Trypanosoma brucei is an extracellular parasite that causes African Sleeping Sickness and is endemic to the sub-Saharan African region. The parasite's extracellular nature forces the parasite to adapt to its host's environment. One of the regulatory mechanisms is to regulate fatty acid synthesis enzymes in response to exogenous fatty acids. Our previous study showed that the insect-host procyclic form (PF) T. brucei regulates the activity and expression level of acetyl-CoA carboxylase (ACC) when grown in media containing different lipid levels. PF in low lipid media has an elevated ACC activity but lower ACC protein level than in high lipid media. We also observed that the addition of C18:0 to PF in low lipid media reduced ACC activity and increased growth rate, which showed an environmental response to the exogenous fatty acid level. Here, we observe the growth and the ACC level of low lipid-adapted PF T. brucei after treatment with fatty acids of different chain lengths. We did not observe a significant change in the ACC protein level. However, we observed significant growth differences with the addition of different fatty acids, and some of these effects were cell density-dependent. These data suggested that the addition of fatty acids changes ACC's activity and PF growth pattern in low lipid, but does not change PF's ACC expression level. Future studies will investigate whether different fatty acids regulate ACC activity by phosphorylation, allosteric regulation, or a combination of both mechanisms.